The present invention generally relates to an image compensating method in a copying machine and, more particularly, to a method for compensating the image developed by a copying machine by simultaneously adjusting both the intensity of light to be projected onto a photosensitive medium and the bias voltage to be supplied to a developer unit.
In order to provide an acceptable copy of an image, it is a conventional practice to independently adjust the intensity of light projected onto the photosensitive medium at the exposure section according to an original or document bearing an image to be reproduced, and adjust the bias voltage to be supplied for the development of the image, to thereby provide compensation for the image being reproduced. Where only the intensity of light projected onto the photosensitive medium is adjusted, a phenomenon occurs in which strokes of characters tend to be reproduced undesirably thick in a low illumination area under the influence of flare, whereas where only the bias voltage is adjusted, a poor copy of the image will be produced from the original because the concentration of a so-called totally blackened area varies.
In order to obviate the above discussed problems inherent in the image compensating methods, Japanese Laid-open Patent Publication No. 58-68766 discloses the image compensating method wherein a single image adjusting dial is utilized for adjusting the intensity of light emitted by an illuminator lamp when turned a certain angle and for adjusting the bias voltage when turned the other angle. However, it has been found that, according to the prior art method disclosed in the above mentioned publication, since the extent to which the image can be compensated when the adjusting dial is turned within the range of angle for changing the intensity of light emitted by the illuminator lamp differs from that when the same adjusting dial is turned within the other range of angle for changing the bias voltage, an acceptable copy of the image cannot always be obtained depending on the type of original or document bearing an image to be copied.